Subnetting


Subnetting is a way to divide networks into more efficient smaller networks. Usually the reasons to subnet networks are security, better use of network address, and improve troubleshooting.

Here is a reference table of the commonly used TCP/IP classes and their subnet masks

Network Class
Beginning Octet
Default Subnet Mask
A
1-126
255.0.0.0

B

128-191

255.255.0.0

C

192-223

255.255.255.0


How to subnet in 5 steps:

  1. Determine the class of your network
  2. Convert the default subnet mask to binary
  3. Determine how many bits you must borrow from the hosts portion of the default subnet mask
    1. Use the following equation: 2n >= Number of subnet
  4. Covert you custom subnet mask to decimal
  5. Find the amount of hosts per network
    1. Use the following equation: 2n-2 >= Number of hosts per subnet

Here you can find more information about subnetting. This is an example of a subnet network before and after.

Original Network Source: Techrepublic
Original Network Source: Techrepublic

Subnet Network Source: Techrepublic
Subnet Network Source: Techrepublic